Scavenge pump for internal-combustion engines



March 24, 1931. w. s. BURN 1,798,010

SCAVENGE PUMP FOR INTERNAL COMBUSTION ENGINES Filed April 16, 1928 6 Sheets-Sheet l flTTO PNEYS March 24, 1931. w. s. BURN 1,798,010

O SCAVENGE PUMP FOR INTERNAL COMBUSTION ENGINES Filed April 16, 1928 I 6 Sheets-Sheet 2 March24, 1931. w. S. BURN 1,798,010

SCAVENGE PUMP FOR INTERNAL COMBUSTION ENGINES Filed April 16, 1928 6 Sheets-Sheet 3 BY MQQM w. s. BURN March 24, 1931.

SCAVENGE PUMP FOR INTERNAL COMBUSTION ENGINES Filed April 16, 1928 6 Sheets-Sheet 4- W. S. BURN March 24, 1931.

SCAVENGE PUMP FOR INTERNAL COMBUSTION ENGINES I Filed April 16, 1928 6 Sheets-Sheet 5 /,v new Tar? 8v ,omlzafid W 4 TOIP/VEYS W. S. BURN Malch 24, 1931.

Filed April 16 1928 6 Sheets-Sheet 6 Patented Mar. 24, 1931 PATENT OFFICE WALTER SCOTT BURN, F HARTLEPOOL, ENGLAND SCAVENGE PUMP FOR INTERNAL-COMBUSTION ENGINES Application filed April 16, 1928, Serial No. 270,526, and in Great Britain December 19, 1927.

This invention relates to scaven e pumps for use in connection with two cycle internal combustion engines and has for its object to provide a scavenge pump which can be timed in relation to the scavenge port operation,

will be balanced in a high degree, will be comparatively light in weight, capable of being conveniently disposed and which will, moreover, be of economical construction.

In accordance with the invention two oppositely disposed horizontal double acting cylinders are employed fitted with trunk pistons which are crank driven, the crank therefor being in turn driven by gearing from the 15 crank shaft of the engine in such manner that the discharge of scavenge air takes place just before the scavenge air ports in the engine cylinder are uncovered by the piston.

In other words a system of timed scavenging 20 with the engine is obtained. In order to facilitate this, it is proposed to drive the scavenge pump at a greater speed than the engine according to the number of cylinders employed. For example, in a three cylinder engine the scavenge pump will operate at three times the speed of the engine, four times, it may be, for a four cylinder engine and five times for a five-cylinder engine. In a six-cylinder engine preferably one or two 0 pairs of pump cylinders will be employed working at three times the speed of the engine. Similarly in an eight-cylinder, two pairs of pump cylinders may be employed working at four times the engine speed, whilst in a nine-cylinder engine, three pairs of cylinders working at three times the speed may be used. All the cylinders will discharge to a common discharge pipe.

The invention will be readily understood 40 from the description now about to be given with the aid of the accompanying drawings which illustrate one specific embodiment.

Of the said drawings, Fig. l is a part sec-- tional end elevation and Fig. 2 a plan of a portion of a four-cylinder engine and applied pump apparatus. Fig. 3 is an elevation at right angles to Fig. 1. Fig. 4: is a view similar to Fig. 3 with certain parts in section and partsremoved. Fig. 5 is a view partly in section on the line 55 of Fig. 1. Fig. 6 is a. diagrammaticview corresponding to Fig. 1 of certain details not shown in that figure, and Figs. 7, 8 and 9 are views similar to Figs. 1, 2 and 5 respectively illustrating a modification. 5.;

. In the example shown in Figs. 1 to 6, the pump is mounted on thefafter bedplate 1 adjacent to the thrust block 2 of the engine so as to minimize space. The pump proper comprises a casing 3 in which are two cylinders at, arranged horizontally at opposite sides of a crank shaft 5, the cylinder axes being parallel but non-aligned in plan to register with a pair of cranks 6 at 180 upon the shaft 5. The cranks 6 are connected by rods 65 7 to trunks 8 upon which pistons 9 are mounted to work in the cylinders 4. By this arrangement it will be observed that the piston and associated parts of one cylinder always move in a direction opposite to that of the piston and associated parts of the other cylinder. Each piston trunk 8 works in a pair of stufiing boxes, -one such stufiiug box 9 being provided in one integral wall 10 of the casing 3 and the other stuffing box 11 being formed in and between a protective housing 12 and a removable end cover 13 for the casing 3. The pump as already stated is double acting, 14 being duplicated passages per cylinder adapted to be alternately placed 3 in communication with the air supply whilst two other passages 15 are adapted to be placed alternately in communication with an air outlet 16. The valves controlling the suction and discharge of air may be of any convenient type but are here illustrated of hollow rotary type, 17 being the suction valve co-operating with one or other of two ports 18 and one or other of the passages 14, and 19 being the discharge valve (Jo-operating with one or other of two ports 20 and one or other of the passages 15 aforesaid.

The crank shaft 5 is driven fromthe engine shaft 21 through ear wheels 22, 23 and the suction valves 1? are driven at the same speed as the crank shaft- 5 each by a gear wheel 24 meshing with the wheel 22. Each discharge valve 19 is driven from the suction valve 17, and at the same speed as W, the latter, through agchain 25 d Sprocket gears 26. The air outlets 16 are connected by a bridge piece 27 to constitute a common discharge. Each air port 18 is shown as communicating with the interior of the bedplate 1 which constitutes a suction reservoir, 28 being air inlet trunks therefor provided with caps 29 and filter screens 30: The wheel 31 shown as secured to the'outer end of the crank shaft 5 primarily servesas-th-e main engine turning wheel but also gives considerable fly-wheel effect to the scavenge pump. The turning: gear, which forms-no part of the present invention is indicated collectively by the numeral In some cases the modification according to Figs. 7, 8 and 9 may be employed where the crankshaft is shown as provided with two chain wheels 32', 33 located at opposite sides'of the turning wheel 3L A chain 34 passing around the wheel 33 under a jockey wheel 35 andaround chain wheels 26 associated with the suction valve-l7 andcompanion discharge valve 19 allows said valves to be drivenin'unison in a simple and direct manner. A. similar chain 34 driven from the chain wheel 32'actuates the remaining pair of suction and discharge valves. Such a modification may be favoured inasmuch as the chain gearing can be located where it is easy of access, 36 being one-of a pair of inspection doors, the other not being shown, through which the jockey wheels 35 can be adjusted.

What I claim is 1. A scavenge pump for the purpose described, comprising a casing; a pair of op posed cylinders therein, each having duplicate air inlets and duplicate a-ir'outlets at opposite ends rotary valves controlling; suctio'n through said duplicate air inlet-s'of each cylinder; similar valves controlling discharge throughthe duplicateair outlets of each cylinder; means driving the second named valves from the first at equal speed therewith; double-acting pistons in said cylinders; a crank-shaft for simultaneously reciprocating said pistons in oppositedirections; an engine shaft and associated gearing driving said crank-shaft at a multiple speed ratio depending uponthe number ofengine cylinders so that discharge impulses of the pump will occur at the scavenging moments of the engine cylinders respectively; and gearing driving the first; mentioned valves from said engine shaft at thesainespeed as said crank-shaft of the pump;

2. A scavenge pump 'fontlie purpose described, comprising a casing; pair of'opposed cylinderstherein having aXes in-i-paral'ilel' relation and-each having a duplicate-ct air inlet and duplicated air-- outlet;-. a: rotary valve for each{ of f saiid cylinders controlling suctionthrough: the: duplicated. air inlet thereof; a sini'ilar valve-tier:eaehiof' saidzcyk inders; controlling 'dischai'ge throu h; are 

